My tsh level is 4.0 but my t3 (liothyronine) and t4 is normal. do i still need meds? and can i be on it during pregnancy?

Depends: First of all, you can be on thyroid med if you are pregnant. Second, with the labs above, you have subclinical hypothyroidism. To treat or not to treat, we have been arguing this for the last few years. I recommend asking your doctor for a thyroid peroxidase antibody test. If this test comes back positive, i would treat to bring TSH to < 2. If it's negative, have a TSH recheck in 3 months.

No treatment needed: You have sub-clinical hypothyroidism. At this level, no treatment is needed. If it should progress to where you need thyroid hormone, it is safe to take during pregnancy.

Depends: During pregnancy, TSH should be less than 2.5. In addition, you should be tested for tpo antibodies. If positive, then treatment is suggested with low-dose levothyroxine to bring TSH less than 2.5. If you do not have positive antibodies, there is no consensus about recommendation, theoretically low-dose levothyroxine could still be an option.

See Endocrinologist: There is emerging data to suggest we should consider treating subclinical hypothyroidism if you have tpo antibodies. It's still just new evidence, and a full discussion with your endocrinologist may be helpful, especially if you fall into category of tpo negative subclinical hypothyroidism- in that case, clinical judgement and your preferences will play a larger role.